It is known to secure a shielding cap within the lamp housing of automotive-type incandescent lamps. The shielding cap partially surrounds the incandescent filament. When using a light source which is not an incandescent filament, however, for example a discharge lamp, this solution is not practical since the high temperatures of the discharge arc result in at least deformation, and, possibly destruction of the shielding cap.
It has been proposed to apply a radiation absorbing coating at the outside of a discharge vessel which should have the same effect as a shielding cap located within the bulb of an incandescent lamp. It has been found that assembly of vehicular or automotive-type discharge lamps having an outer shielding coating results in heat distribution which is unsatisfactory and which interferes with long lifetime of the shielding coating.